A.slack enough to allow slight leakage of fluid
B.slightly clocked
C.brought up tight so as not to allow any leakage
D.fitted with a relief valve
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A.Volute pump
B.Diffuser pump
C.Regenerative pump
D.All of the above
A.mixed-flow
B.axial-flow
C.centrifugal
D.displacement
Which of the following operating features do displacement pumps bear if they are working under no-cavitation condition?（）
(1) output is almost directly proportional to speed
(2) they are self-priming
(3) they will develop a discharged pressure equal to the resistance to be overcome, irrespective of speed
A.（1）and（2）
B.（2）and（3）
C.（1）and（3）
D.（1），（2）and（3）
Which of the following pumps will build up a bursting pressure or stall their motors if the discharge valves are closed?（）
(1) gear
(2) centrifugal
(3) screw
A.（1）and（2）
B.（1），（2）and（3）
C.（1）and（3）
D.（2）and（3）
A.providing the impeller with balancing holes
B.the use of symmetrical impeller
C.neither A nor B
D.either A or B
最新試題
An internal bypass is provided on some hydraulic system suction strainers to help reduce the possibility of （）.
A pressure drop through the refrigerant liquid line may cause （）.
When the steering gear is in operation, you should （）.
If the suction pressure at the refrigeration compressor is below normal, the cause can be（）.
The usual symptoms of cavitation in a centrifugal pump is （）.
An increasing head pressure in a refrigeration system, without any corresponding change in the cooling water inlet temperature, would probably be caused by （）.
A grease gun is generally used to lubricate a （）.
Which of the listed pumps is NOT a positive displacement pump?（）
One cause of high head pressure occurring in a refrigeration system can be （）.
The amount of fluid friction or internal friction inherent in a mineral lubricating oil is reflected as a measure of its （）.